A storage system is a computer that provides storage service relating to the organization of information on writable persistent storage devices, such as memories, tapes or disks. The storage system may be deployed within a storage area network (SAN) or a network attached storage (NAS) environment. When used within a NAS environment, the storage system may be embodied as a file server including an operating system that implements a file system to logically organize the information as a hierarchical structure of directories and files on, e.g., the disks. Each “on-disk” file may be implemented as a set of data structures, e.g., disk blocks, configured to store information, such as the actual data for the file. A directory, on the other hand, may be implemented as a specially formatted file in which information about other files and directories are stored.
The file server, or filer, may be further configured to operate according to a client/server model of information delivery to thereby allow many client systems (clients) to access shared resources, such as files, stored on the filer. Sharing of files is a hallmark of a NAS system, which is enabled because of semantic level of access to files and file systems. Storage of information on a NAS system is typically deployed over a computer network comprising a geographically distributed collection of interconnected communication links, such as Ethernet, that allow clients to remotely access the information (files) on the filer. The clients typically communicate with the filer by exchanging discrete frames or packets of data according to pre-defined protocols, such as the Transmission Control Protocol/Internet Protocol (TCP/IP).
In general, NAS systems utilize file-based protocols to access data stored on the filer. Each NAS client may therefore request the services of the filer by issuing file system protocol messages (in the form of packets) to the file system over the network. By supporting a plurality of file system protocols, such as the conventional Common Internet File System (CIFS), the Network File System (NFS) and the Direct Access File System (DAFS) protocols, the utility of the filer may be enhanced for networking clients.
A SAN is a high-speed network that enables establishment of direct connections between a storage system, such as an application server, and its storage devices. The SAN may thus be viewed as an extension to a storage bus and, as such, an operating system of the storage system enables access to stored information using block-based access protocols over the “extended bus”. In this context, the extended bus is typically embodied as Fibre Channel (FC) or Ethernet media (i.e., network) adapted to operate with block access protocols, such as Small Computer Systems Interface (SCSI) protocol encapsulation over FC (FCP) or TCP/IP/Ethernet (iSCSI).
SCSI is a peripheral input/output (I/O) interface with a standard, device independent protocol that allows different peripheral storage devices, such as disks, to attach to the is storage system. These storage devices may be locally attached to the storage system or, in the case of a SAN environment, attached via a network. In SCSI terminology, clients operating in a SAN environment are initiators that initiate requests and commands for data stored on the storage devices. The storage system is a target configured to respond to the requests issued by the initiators in accordance with a request/response protocol. The SAN clients typically identify and address the stored information in the form of blocks or disks by logical unit numbers (“luns”).
In SCSI addressing, each initiator has a world wide name (WWN) or iSCSI name that is used by the initiator to access a lun entity, such as a disk, on the storage system. For example, each system on a FC SAN has a WWN, which is a 64-bit location independent identifier (ID) that is written in hexadecimal notation; iSCSI names are analogous to WWNs, but with a different format. The iSCSI names are used with the iSCSI protocol as IDs when restricting block-level access to a lun by one or more initiators. Thus, each time an initiator desires access to a lun, the WWN ID or iSCSI name must be provided to the storage system by a client/user of the initiator. This is an inefficient and possibly error-prone approach to accessing luns on a SAN storage system.